Liver fibrosis is the common response to chronic liver injury, ultimately leading to cirrhosis and its complications, portal hypertension, liver failure and hepatocellular carcinoma. The fibrogenic process is consecutive to intense proliferation and accumulation of hepatic myofibroblasts that synthesize fibrosis components and inhibitors of matrix degradation (Friedman, S. L., J Biol Chem 275, 2247-50 (2000)).
Cannabis Sativa contains over sixty compounds, the most active of which is (-) Δ9-tetrahydrocannabinol (THC). Endogenous natural cannabinoids have also been characterized, anandamide and 2-arachidonyl glycerol, which are arachidonic acid-derived lipids (Piomelli, D et al, Trends Phamacol Sci 21, 218-24. (2000)). Cannabinoids bind to two G protein-coupled receptors, CB1 and CB2, that equally bind THC (Pertwee, R. G., Curr Med Chem 6, 635-64. (1999)). CB1 is thus one of the two known cellular receptors for cannabinoids. This receptor being a G protein-coupled transmembrane receptor is known to be expressed in brain and blood vessels (Pertwee, R. G., Curr Med Chem 6, 635-64 (1999)) but not in hepatocytes (Guzman, M and Sanchez, C., Life Sci 65, 657-64 (1999)). CB1 mediates the psychoactive effects of cannabis. In contrast, CB2 receptors are mainly expressed in the immune system and are devoid of psychoactive effects (Friedman, S. L., J Biol Chem 275, 2247-50 (2000)). In addition to their psychotropic effects, cannabinoids display analgesic, antiemetic and orexigenic central effects (Harrold, J. A. and Williams, G. Br J Nutr 90, 729-34 (2003)). Moreover, cannabinoids also elicit anti-inflammatory and vasorelaxing properties (Kumar, R. N., Chambers, W. A. and Pertwee, Anaesthesia 56, 1059-68. (2001)). Several studies also suggest that cannabinoids may be potential antitumoral agents, owing to their ability to induce the regression of various types of experimental tumors, including glioma or skin tumors. These antitumoral effects are mainly attributed to their antiproliferative and apoptotic properties (Bifulco, M. et al., Faseb J 29, 29 (2001); Casanova, M. L. et al., J Clin Invest 111, 43-50. (2003); Sanchez, C. et al., Cancer Res 61, 5784-9. (2001)).
There are only few data concerning the hepatic action of cannabinoids. CB1 and CB2 receptors are not expressed in hepatocytes (Guzman, M. and Sanchez, C. Life Sci 65, 657-64 (1999)). However, CB1 receptors are present in endothelial cells isolated from hepatic arteries, and their expression increase during cirrhosis (Batkai, S. et al. Nat Med 7, 827-32. (2001)).
Two isoforms of the receptor CB1 have been isolated: a long isoform (corresponding to SEQ ID NO:1) and a shorter one truncated in the NH2 terminal part corresponding to a splice variant (corresponding to SEQ ID NO:2), which differ in their affinity for their ligands (Shire et al., J Biol Chem, (1995); Rinaldi-Carmona et al, J Pharmacol Exp Ther (1996)). There also exist 5 single nucleotide polymorphisms in the coding region of the CB1 receptor gene. Of these only three result in single amino acid changes to the CB1 receptor (these being, in SEQ ID NO:1, a Phenylalanine to Leucine substitution at position 200, an Isoleucine to Valine substitution at position 216 and a Valine to Alanine substitution at position 246 and the corresponding positions in SEQ ID NO:2). A consensus 7-domains sequence for the CB1 receptor exists which is strongly conserved in vertebrates but does not appear in other cannabinoid receptors (Attwood, T. K. and Findlay, J. B. C., Protein Eng 7(2) 195-203 (1994), Attwood, T. K. and Findlay, J. B. C., 7TM, Volume 2 Eds G. Vriend and B. Bywater, (1993), Birnbaumer, L., Ann. Rev Pharmacol Toxicol, 30, 675-705 (1990), Casey, P. J. and Gilman, A. G., J. Biol. Chem. 263(6) 2577-2580 (1988), 5. Attwood, T. K. and Findlay, J. B. C, Protein Eng 6(2) 167-176 (1993), Watson, S, and Arkinsall, S, In The G Protein-Linked Receptor Factsbook, Academic press, 1994, PP 80-83). That consensus amino acid sequence comprises the 7 protein domains of SEQ ID NO:3 to SEQ ID NO:9.
Antagonists to the receptor CB1, which include reverse or inverse agonists, have been previously described. These include the substituted amides described in WO03/077847, the substituted aryl amides described in WO03/087037, the substituted imidazoles described in WO03/063781, bicyclic amides described in WO03/086288, the terphenyl derivatives described in WO 03/084943, the N-piperidono-3-pyrazolecarboxamide and N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3- -carboxamide described in EP-B-656354, the aryl-benzo[b]thiophene and benzo[b]furan compounds respectively described in U.S. Pat. No. 5,596,106 and U.S. Pat. No. 5,747,524, the azetidine derivatives described in FR2805817, 3-amino-azetidine described in FR2805810, or the 3-Substituted or 3,3-disubstituted 1-(di-((hetero)aryl)-methyl)-azetidine derivatives described in FR2805818. These documents are incorporated herein by reference. Other antagonists are commercially available such as N-(piperidin-1-yl)-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-1H-py-razole-3-carboxamide, known commercially as AM251 and the compound known as LY-320135.
Uses of these CB1 receptor antagonists are known for the treatment of sexual dysfunction (patent application WO 03/082256), or diarrhoea (patent application WO 01/85092), or neuro-inflammatory diseases or substance abuse disorders, obesity, asthma, constipation (patent application WO 03/077847).
Documents U.S. Pat. No. 5,939,429, WO 03/077847, WO 03/084930, WO 03/084943, WO 03/063781 and WO 03/087037 disclose that CB1 antagonists can reverse the systemic hemodynamic alterations in rats with cirrhotic portal hypertension.